Catalytic conversion of hydrocarbons and regeneration of fouled catalyst in stages



May 2, 1950 K. M. WATSON 2,506,122

CATALYTIC CONVERSION OF HYDROCARBONS AND REGENERATION Y 0F FOULED CATALYST IN STAGES Filed June 27, I947 LOUVERS CONVERSION PRODUCTS CONVERSION PRODUCTS SEALING AND STRIPPING GAS v FLUE GAS SEALING AND STRIPPING GAS FLUE GAS FLUE GAS STEAM STEAM WATER 28 FRESH :1 W

CATALYS REGENERATOR AIR ST EA WAT H AT EXCHANGER 23 33 20 3 CHARGE OIL INVENTOR KENNETH MERLE WATSON ATTO R N EYS Patented May 2, 1 950 CATALYTIC CONVERSION OF HYDROCAR BONS AND REGENERATION OF FOULED CATALYST IN STAGES Kenneth Merle Watson, Madison, Wis., assignor to Sinclair Refining Company, New York, N. 1 a. corporation of Maine Application June 27, 1947, Serial No. 757,640

- This invention relates to the pyrolytic conversion of hydrocarbons and, more particularly, to pyrolytic conversion processes involving the use of a solid catalyst. v

. In such operations, a carbonaceous deposit is formed on the solid catalyst during the hydrocarbon conversion and the catalyst'must be periodically regenerated to restore its catalytic eifectiveness.

In one method of operation previously proposed, the hydrocarbon to be converted is passed continuously upwardly through a downwardly gravitating bed of catalyst, in granular or pelleted form, in a vertically elongated conversion chamber of large transverse dimension, the cat alyst being continuously withdrawn from the lower end of the chamber, regenerated, and returned to the upper end of the chamber. The regeneration is eflfected by burning off the carbonaceous deposit by passing the hot catalyst downwardly through a similar vertically elongated chamber countercurrent to a stream of air. i

Such operations have entailed expensive and troublesome mechanical elevator means for conveying the catalyst from the lower end of the conversion chamber to the top of the regenerating chamber and again from the lower end of the regenerating chamber to the top of the conversion chamber. Difliculties have also been experienced in effectinguniformcontact between the hydrocarbon vapors and the catalyst by reason of the tendency of the vapors to channel upwardly through the bed of catalyst. Similar difficulties have been experienced in the regenera tion of the catalyst. The present invention provides an improved method of. operation whereby these difilculties are avoided.

In accordance with my present process, the catalyst at an elevated temperature is caused to gravitate as a continuous, vertically elongated bed, or column, downwardly through a vertically elongated chamber having at least one relatively narrow horizontal dimension. The conversion reaction, and also a. substantial amount of regeneration of the catalyst, are successively efiected in this single elongated body of catalyst. The catalyst is passed from the bottom of the column to a regenerating chamber wherein residual carbon is burned from the catalyst, and also any catalyst fines formed by attrition are separated from the catalyst, by blowing with additional air.

The hot regenerated catalyst is passed from the regenerating chamber. into a stream of hydroparbon vapors to be processed and is caught up 3 Claims. (Cl. 196-52) by the vapors and carried in suspension upwardly into an enlarged chamber, positioned at an elevation higher than the upper end of the elongated chamber, and in which the catalyst drops out of suspension and flows therefrom by gravity onto tghe upper end of the vertically elongated catalyst The hydrocarbon vapors separated from the catalyst pass from the enlarged chamber and are repeatedly passed back and forth through the upper portion of the hot catalyst bed, at progressively diil'erent elevations, whereby conversion 01" the hydrocarbons is efiected with the resultant deposition of carbonaceous material on .the' catalyst. V v Air, or other oxidizing gas, is similarly passed back and forth through the lower portion of the hot catalyst bed at progressively difierent elevations, with a resultant burning of! from the catalyst of a substantial portion of the carbonaceous deposit.

The hot, partially regenerated catalyst, as previously noted, is withdrawn from the lower pot-L tion of the vertically elongated chamber, 'sus-. pended in a gaseous carrying medium, advantageously air, and carried in suspension to the separate regenerating chamber, wherein residual carbon is burned from the catalyst by contact with air and from which the regenerated catalyst is returned to the vertically elongated catalyst bed, as just noted. Heat for efifecting the conversion is supplied in large measure, by the burning of the carbonaceous deposit. Additional heat may be supplied where required by preheating the hydrocarbon charge oil vapors.

Catalystfines formed by attrition during the cycling of the catalyst are carried ofi from the cycle in suspension in flue gases passing from the zone of final regeneration.

The hydrocarbon vapors to be converted may be I passed through the catalyst bed, at" progressively higher or progressively lower levels, that is, in a generally countercurrent or generally concurrent direction with respect to the direction of the catalyst flow. Similarly, air for use in the partial regeneration of the catalyst may be passed through the lower portion of the catalyst bed at progressively higher or progressively lower levels. Due precaution should be taken, however, to minimize intermixing of regeneration gases and hydrocarbon vapors.

The effecting of the regeneration of the cat:- alyst in stages, as just described, provides a particularly advantageous method of removing catalyst fines from the cycle, and a very complete and uniform regeneration of the catalyst is effected. Further, means are provided whereby excess air may be passed in contact with the catalyst in the final regeneration to insure complete removal of carbonaceous deposit without danger oi excessoxygenbecoming admixed with the hydrocarbon vapors.

In a particularly advantageous method of operation in accordance with my invention, the hydrocarbon vapors are repeatedly passed through the column of catalyst, at progressively lower levels in the upper portion of the catalyst bed, and the regeneration air is passed through the catalyst, at progressively higher levels; iii-the lower portion of the catalyst bed. By this tre cedure, a zone of low pressure is created at the intermediate portion of the bed, both with re: spect to the hydrocarbon vapors, and the gaseous products of the combustion, and the tendency of the gases and vapors to become intermixed is minimized;

It is'*- also particularly advantageous toinject' iii-lie sealing; or stripping, gas into the zone interniediate the conversion and regenerating sec'- tion's'. This serves, further, to prevent mixing of combustion gases and hydrocarbon vapors and also serves as a stripping medium for stripping from the spent catalyst readily vaporiz'able hydrocarbons.

A large amount of heat isliberated in the burniiig' or the carbonaceous depositand care should exercised to avoid overheating of the catalyst. It is usually advantageous to e'iitract heat from the" beds of catalyst undergoing regeneration in an amount sufficient to avoid excess temperatii r's. For this purpose, cooling coils may, with advantage, be provided in the regenerating seetl'ofi of the vertically elongated bed of the catalyst and water, or other cooling fluid circulated theretYifbu'gh. Also, a portioli or the catalyst may be withdrawn from the bed of catalyst undergoing final regeneration, cooled by passing through a waste heat boiler, or the like, and returned to the bd of catalyst. I

By proper control of the rate or downwardflow (if the catalyst bed and coordinating therewith traits of new and number or passes of the by Q arbon vapors and regenerating air there: t the catalyst will e substantially spent 5nd eady for regeneration by the time it reaches the owe end or the reaction zone and a: maJ'Qr id n of-thecarbofiaceous deposit formed there- 3 will be burned off updn reac ingthe lower fi'd 6f the regenerating Zone or the catalyst colu The optimum fate or downward new of the fiatalyst bed will depend rimarily iiporithe' typ of catalyst employed, the type of 'l'iydi'oc'a'rb'on being converted, operating temperatures, therate of hydrocarbon feed, the -ei'ite'nt of the required feactien, the depth of cracking, for instance, the iiuinber 6f passes through the catalyst and the thickness of the catalyst bed. The optimum rate of catalyst flow for anylp'articula'r operation is FadiIy determinable by simple tests and with advantage, controlled by regulation of new of Eata1y'st from the 1wer end or the regenerating fififie by means of a suitable valve arrangement. By effecting the finalregen eration or the catalyst in a separate chamber, as'just desc ibed, there generation of the catalyst may be controlled ddridently of the rate of downward flow of the vertically elongated catalyst bed. V v The process is applicable to-various'type of Hydrocarbon conversionand contemplatesthe use of various solid catalysts in granular or pelleted form. However, the invention will be more particularly described and illustrated with reference to the accompanying drawings Figure 1 of which represents, somewhat conventionally, an embodiment of the invention in a catalytic cracking process carried out in a particularly advantageous type of apparatus subject ofmy copending application, Ser. No. 757,647, filed concurrently herewith, in which the column dicatalyst is in the form of a vertically elonted a nu us; nd

Figure 2 is a transverse section along the line 2-? oi Figure 1.-

In the drawing, the part indicated by the referefrc'e' numeral l" is a cylindrical casing, advanta'geous'ly of sheet metal, enclosed at its upper end. Coaxially positioned in casing I are cylindrical casings 2, 3, and 4 of progressively smaller diameters which, together with the outer casing, form annular chat-titers 5, and l and an interior cylindrical portion 8'. The intermediate annulus 6 is substantially unobstructe for its en'tir height. The outer annulus 5 completely ob-' structedby a plurality ofverticall spaced partitioris a of considerable depth, forming a pmfalityof'vertical-ly spec'edfenamterg H). The inner ennui-us T is similarly dividedinto a pmmnty or vertically spaced chambers II by similar parti= tions or spacers 1 [2;-

Each of the chambers [0' and H- is connected with the annulus '6 through louvei's, the slats of which project upwardly and outwarm from the annulus B'into th resneet ve the-meets.

The casings 2; 3* and 4 terrain-ate short tithe upper end or the cylinder for ed by tes ing i so as to form alar ge" c'yli dric I chamber 13 the upper portion oftheapparatus. Th uppermost of chambers It is in operrcommunication at its upper end with chamber [3. The annulus t 1s, likewise, in open communication its upper end with chamber [3. The upper end of the upper mo t chamber I l and the upper erra of the inner cylinder 8 are closed ofi from chamber i3 by means (if partition 14; elevator conduit 15 eX'te'nd's upwardly throliglithe inner chamber 8 and leads into chamber It through an opening in partition 54. The lower" end or elevator con drill; l connected with a source of vaporized charge oil, not s'hdwn', andalso through conduit It with the lower portion or a regenerator H, which regenerator may be of conventional type. The lower end or annulus s o ensinto a conical opper member [8, he lower ends "of which a e t'tnnecteaty conduit 139* with conduit at which is,

in turn, connected with tne lower end of conical member 2| forming the lower portion of the 'en a f lt; The conduit :9 may beprovide d with valves 22', which be of cdr'ivjentional type, advan tag'eously a conventional slide valve, for regulating and eont'renmg the new or catalyst through conduit [9. 1 if 'rh 'spaeers, er partitionst and #2 are, with advantage, positioned somewhat as shown" in the drawing so as to form l0 and" H in staggered positions such tnat'tne lower end of a given chamber to is directly opposite the upper end r the neizt lower ens-int r If and the lower end of said cl'iarriber l l is directly opposite the upper end of the next ltwer chamber-m; The spacers!) and i2 are, for clarity, 'showh'in the drawing as solid eeetiet's; but'itis to be" understood that they may be either S'dlid 6r hollow, Further,-foi" raeetitfiweight and mine-term used in fabrication, the respective casings I and 4 may be discontinuous at the points of the respective spacers.

3 In operation, the annulus 6 is filled with granular catalyst, for instance, by charging the catalyst through an opening, not shown, in the top of the apparatus, adapted to be sealed in operation. vaporized hydrocarbon oil to be processed is charged through line I5 in which it picks up in suspension, catalyst passing downwardly from the regenerator I1 through conduit I6 at a rate controlled by adjustable valves 23. The hydrocarbon vapors carrying the catalyst in suspension pass upwardly through the elevator conduit I5 into chamber I3 wherein the catalyst drops out oi. suspension by reason of decreased velocity of the vapors and falls onto a bed of catalyst maintained in chamber I3 from which the catalyst flows into the annulus 6, keeping it continuously filled with the catalyst.

Separated hydrocarbon vapors pass from chamber I3 into the upper end of the uppermost chamber I and, from thence, the vapors pass, by way of the louvers, through the bed of.catalyst in annulus 6 and into the upper end of the uppermost chamber I I. From the lower portion of said chamber II, the vapors pass back through the 'body of catalyst into the next lower chamber I0, and so back and forth through the body of catalyst, at progressively lower levels, until the vapors reach an intermediate chamber ID from which they are withdrawn through one of the valved lines 24 to a fractionating apparatus, not shown. In the drawing, a plurality of conversion product draw-off lines 24 are shown leading from progressively lower chambers III. This is advantageous as it permits withdrawal of conversion products at selective levels from the reaction zone thereby varying the space velocities of the operation and also varying the depth of the intermediate sealing and stripping zone, subsequently described.

The catalyst which has been substantially spent continues downwardly through annulus 6 and is stripped of readily vaporizable hydrocarbons remaining thereon by a stripping gas or vapor, steam, for instance, introduced into a still lower chamber I0 through lines 25.

Air is passed into the lowermost chamber III through lines 26, flows therefrom by way of the .louvers, through the bed of catalyst into the lowermost chamber 5 I and back through the catalyst into the next higher chamber II], and so back and forth through the catalyst, at progressively higher levels, until it reaches an intermediate chamber I0, below that into which the stripping medium is injected, and the flue gases pass therefrom through conduits 21 to a stack, not

shown in the drawing.

T The air passing in contact with the hot catalyst results in the burning of the major portion of the carbonaceous deposit formed on the catalyst during the hydrocarbon conversion. Excess heat is extracted from the catalyst undergoing regeneration by means of cooling coils 28, extending .through the bed of catalyst in annulus 6 and through which a cooling medium is circulated. For instance, water may be circulated through the cooling coils and thereby converted into steam. Any number of cooling coils may be used to extract from the catalyst an amount of heat necessary to prevent excessive temperatures.

The partially regenerated catalyst passes from .the lower end of the regenerating zone through perforations in a series of distributing plates 29 so po itioned as to permit the now of catalyst therethrough. at a retarded rate, dependent upon the angle of repose of the catalyst, and also to retard the passage of air upwardly therethrough from conduit 20, as understood by the art. From thence, the catalyst flows through the annular connection 30 into hopper I8 and through the conduit I9 intothe stream of air passing through conduit 20 and is carried thereby in'suspensioiiupwardly into the regenerator I1.

The regenerator I1 may be of conventional type and may be provided with means for cooling'the body of catalyst undergoing regeneration by continuously withdrawing a portion thereof through conduit 3 I, cooler 32, advantageously a waste heat boiler, and conduit 33 into the stream of air passing to the regenerator I1 through conduit 20 and is returned to the regenerator I1 in suspension in the air, together with partially regenerated catalyst from theannulus 6. 7

Residual carbon is burned from the catalyst in the regenerator I'I'and the products of combustion pass from the upper end through cyclone type separator 34, for the separation of coarser particles of suspended catalyst, which are returned to the dense phase body of catalyst in the chamber,

'and the products of combustion passed therefrom carrying catalyst fines in suspension through conduit 35 to a precipitator or stack, not shown in the drawing. Fresh catalyst may be supplied as required during operation through conduit 36 at a rate controlled by valve 36a.

The rate of iiow of the catalyst from the lower end of catalyst bed in annulus 6 may also be controlled and regulated, in conjunction with plates 2-9 and valve 22, or in lieu thereof, by means of a valve arrangement positioned just below the annular connection 30. This valve mechanism comprises an annular flat ring member 31 of somewhat greater width than the annulus 30, positioned directly below and spaced from the lower end thereof. The ring 31 is adjustably supported by a plurality of shafts 38 extending downwardly through the wall of hopper I8 and sealed by suitable glands 39. The lengthof the shafts 38 may be adjusted by means of turn buckles 40 and the lower ends of the shafts are connected by linkages 4| to eccentrics 42. The

eccentrics 42 are connected by suitable means,

not shown, so that they will operate together to impart an oscillatory motion to ring 31, adjust ment in level of ring 31 and. of its distance from the lower end of annulus 30.being made by the turn buckles 40.

In the valve arrangement shown, the ring 31 will completely shut 011 the flow of catalyst without requiring mechanical seating of the valve.

.By raising the ring to a point where its edges depending upon other operating conditions. Generally, its thickness is, with advantage, about 1 to 2 feet. The depth of the spacers 9 and I2 is, with advantage, at least equal to, or somewhat greater than, the thickness of the bed of catalyst in annulus 6 so as to minimize any tendency of the gases or vapors to pass directly fromone chamber to that immediately above or belQ?i..it

a,-suewe :irjatner than through the catalyst :be'drto the opior lconvenie'nce, the vertical spacing between he'foutersand inner annular chambers, respec- *tively, is shown, intsomeiinstancea in the drawing as only slightly greater than the thickness ofthe atalyst bed in annulus '6. It will'be understood =thatthez spacingsi'are not iintendedsto be drawn to scale and are; with advantage,"ofgreater'rela xtive vertical dimensiona than ShOWIlIiIl the (draw- "advantageously being greater Tthan -the "thickness oi thea'catalystbed as previously noted. .4 .With the exceptiongof the intermediate zone, tsome by passin of the gases or yaporsfromone acne to the next:hig her or lower zon'edoes not {seriously interfere with the operatiom However, mixing of combustion gases from the regeneratmg 1zone withthe hydrocarbon vapors should usually be avoided and for'this reason; it isparticularly advanta e us t a the spa n just above; t :regeneratingzone be substantially greater than the path horizontally through the catalyst bed. a :The apparatus specifically shown in the drawinggprovides for-four to sixpasses of-the hydrocarbon vapors and for four passes of the regenerating air through the catalyst bed. Freguently, a-greaternumber of p sses is desirable sandisiwithin the contemplation of my invention. ifgurel of! the drawing is somewhat fragmentary, indicating-intervening sections of the apparatus of similar design.

The "injection of sealing or stripping gas betweenethe conversion and regenerating zones may 7 fluently be omitted particularly Where the encounter airpassed through theregenerating is so controlled that upon reachingfthe ,upperfendlof'the regenerating zone, the combusftion gases are substantially "free from uncombine'd oxygen. Under such, conditions, thehot Tiner't combustion products will serve to strip the go." s may be permitted to pass upwardly through strippingz'one into the conversion zone'by i posing a slight'back pressure on the efiluent ega ses.

The invention contemplates the use or various "typeset catalyst,ior'instance, natural orsynth 'earths, silica'gel, andthe like, or various "inert carriers having active catalysts deposited "thereon. The size of theparticles of-catalyst is, fth advanta'ge, of a mesh within the range'of 25 -o -40,'th'ough catalysts of larger or smaller 'particle 'size may beemployed. 'Pelleted catalyst as coarse as e to 10 mesh may be employed with 'advantage. USually, powdered catalyst, u as *iise'd'in-the 'fiuid'catalyst processes, is'less desirable because of a tenden'cy'of the catalyst particles" to be carried out of the catalyst bed along withthe gaseszand vapors, butinay be used in :eou' uncuon with-relativelow'gas and vapor ve- 'l'ocities thr'ough'the catalyst bed.

Operating'conditions are generally subject'to "cons'i derable variation depending upon the particirl'af catalyst' employed, and'the nature and "the Spent catalyst and a portion of the combustion "The elevator conduit 55 is, with advantage, of

ar brou ht-i icenta' ma beumaintein d re el uni orm Fur er e xee e lrun T :provenient' which comprises passing the c'atal t yerselythrou'gh the body ofca'talyst in-a lo '1' "extent of :the desired reaction. Inzcrfacklng oil, for instance, using-a silica-alumina type-cattle lyst, the temperature of the reaction zone is,zwith advantage maintained withinvthe range of about 7501te95091E and the; pressure within the; range ofiaboutlo to .l5lpoundsc-per square inch. :In-the regenerating Zones, a a" temperature within the ranged-906 to' 115011. isusually,satisfactory.

The --teinperature 1 in the reactionaone is: con trollediir large: measure: at least bythe tempera:-

ture of -the catalyst andthe. prohortionthereofintroduced :into the. charge} oil and also the extent of preheat of the charge oil. ,ZIhe temperature :of the catalyst under o n e era o is con: trolled by ithe .gextraction of heat therefrompaii previouslygdescribed; any desired number; of c9015 ing coils beingused forithat purpose; intheregencrating ,zoneof annulus =5 and any number of f le s or wast 1 eat boilersbeing used in on nection with the final regeneration inregenera tor 1 ll.

:By the 1 presen p e es he ex ent o con ac b we n the catalystandthe droc rbon vapors being convertedand also the catal ticacti-vity of he 'e aly twith which th hyd eca envenere form and: complete; regeneration ofthe catalyst is attained-and the catalyst is efiectivelyl freed-from catalyst fines in the final regenerating step'. ZI'he p ificess has the advanta ef: gh. l f iformit ifli the product, increased catalyst. life; and catalytic efieet ven a ne ee i'e eQQIlQ Y- Operation by on of the eliminationof mechanical conveyn'd also anexceptionally'close f' contr'ol of 6pi claim? .1. In'aprocessffor the pyrolyticconversionof hydrocarbons wherein'ithe hydrocarbons in vapor .phase are continuously passed in intimate con:

tact with a so 1d catalystatf an elevated tem era ,ture, esu ting intheformati n of a carbonaceous deposit outhe catalyst, and-in which thecatalyst is'i'ritermitt'ently regenerated by u ni dff the c' bnaceous deposit byc'ontact with air; the

in a relatively "narrow, Verticjallyf elongated body wnwa d y-th ou h n en losed ver l elonigated chamberjefiecting' the conversion of "the hx 'rocar ns by re ea edly pass n the hydro;-

a bon vapors t ansve sely r us'h hj 'bedy'e je ystin t -u per zone. o h hamb a efs am ne the' rd ca e a s r it e. atal t arra ;1vree ne a m t e a s t b t u usv a d ep ate Pa s n e e e g i sivfelydifferentelevations, and thereafter z'oneof the chamber'at progi essivelydifiernt' tie. vations and withdrawing the gaseous products of the; 'regeiierationfrom the system, withdrawing partially regenerated hot catalyst from the lower 'verte'd; i

'{ln a=process for the pyrolytic conversion of hydrocarbons wherein'the hydrocarbons in vapor phaseareconunuousiy passed inintimate contact witha solid catalyst at an" elevated temperature,

resulting'in; the formation of a carbonaceous deposit (iii the catalyst, and in-which'thecatalyst intermittently regenerate'd'by burning offlthe cabbonaceous deposit by contact with air, the improvement which comprises passing the catalyst in a relatively narrow, vertically elongated body downwardly through an enclosed vertically elongated chamber, effecting the conversion of the hydrocarbons by repeatedly passing the hydrocarbon vapors transversely through the body of catalyst in an upper zone of the chamber at progressively different elevations, and thereafter separating the hydrocarbon vapors from the catalyst, partially regenerating the catalyst by continuously and repeatedly passing regenerating air transversely through the body of catalyst in a lower zone of the chamber at progressively different elevations and withdrawing the gaseous products of the regeneration from the system, withdrawing partially regenerated hot catalyst from the lower end of the chamber, suspending it in air and passing it in suspension to a final regenerating zone in which residual carbon is burned from the catalyst by contact with the air, withdrawing regenerated catalyst from the last said zone, suspending the regenerated catalyst in hydrocarbon vapors to be converted and passing the suspension upwardly into an enlarged chamber at an elevation higher than the upper end of the vertically elongated bed of catalyst, separating the catalyst from suspension in said chamber, and passing it by gravity onto the upper end of the vertically elongated body of catalyst and passing the hydrocarbon vapors through the catalyst as described.

3. In a process for the pyrolytic conversion of hydrocarbons wherein the hydrocarbons in vapor phase are continuously passed in intimate contact with the solid catalyst at an elevated temperature resulting in the formation of the carbonaceous deposit on the catalyst, and in which the catalyst is intermittently regenerated by burning off the carbonaceous deposit by contact with air, the improvement which comprises passing the catalyst in a relatively narrow vertically elongated body downwardly through an enclosed, vertically elongated chamber, effecting the conversion of the hydrocarbons by repeatedly passing the hydrocarbon vapors transversely through the body of catalyst in an upper zone of the chamber at progressively lower elevations and thereafter separating the hydrocarbon vapors from the catalyst, partially regenerating the catalyst by continuously and repeatedly passing regenerating air transversely through the body of catalyst in a lower zone of the chamber at progressively high elevations and withdrawing the gaseous products of the regeneration from the system, withdrawing partially regenerated hot catalyst from the lower end of the chamber, suspending it in air, passing it in suspension to a final regenerating zone in which residual carbon is burned from the catalyst by contact with air, withdrawing regenerated catalyst from the last said zone and returning it to the upper end of the catalyst bed in suspension in hydrocarbon vapors to be converted.

KENNETH MERLE WATSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,376,365 Lassiat May 22, 1945 2,418,679 Utterback Apr. 8, 1947 2,425,849 Voorhees Aug. 19, 194'! 

1. IN A PROCESS FOR THE PYROLYTIC CONVERSION OF HYDROCARBONS WHEREIN THE HYDROCARBONS IN VAPOR PHASE ARE CONTINUOUSLY PASSED IN INTIMATE CONTACT WITH A SOLID CATALYST AT AN ELEVATED TEMPERATURE, RESULTING IN THE FORMATION OF A CARBONACEOUS DEPOSIT ON THE CATALYST, AND IN WHICH THE CATALYST IS INTERMITTENTLY REGENERATED BY BURNING OFF THE CARBONACEOUS DEPOSIT BY CONTACT WITH AIR, THE IMPROVEMENT WHICH COMPRISES PASSING THE CATALYST IN A RELATIVELY NARROW, VERTICALLY ELONGTED BODY DOWNWARDLY THROUGH AN ENCLOSED VERTICALLY ELONGATED CHAMBER, EFFECTING THE CONVERSION OF THE HYDROCARBONS BY REPEATEDLY PASSING THE HYDROCARBONS VAPORS TRANSVERSELY THROUGH THE BODY OF CATALYST IN AN UPPER ZONE OF THE CHAMBER OF PROGRESSIVELY DIFFERENT ELEVATIONS, AND THEREAFTER SEPARATING THE HYDROCARBON VAPORS FROM THE CATALYST, PARTIALLY REGENERATING THE CATALYST BY CONTINUOUSLY AND REPEATELY PASSING REGENERATING AIR TRANSVERSELY THROUGH THE BODY OF CATALYST IN A LOWER ZONE OF THE CHAMBER AT PROGRESSIVELY DIFFERENT ELEVATIONS AND WITHDRAWING THE GASEOUS PRODUCTS OF THE REGENERATION FROM THE SYSTEM, WITHDRAWING PARTIALLY REGENERATED HOT CATALYST FROM THE LOWER END OF THE CHAMBER, SUSPENDING IT IN AIR AND PASS- 